//------------------------------------------------------------------------------
// <copyright file="ColumnBinding.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------

namespace System.Data.OleDb {

    using System;
    using System.Diagnostics;
    using System.Data;
    using System.Data.Common;
    using System.Globalization;
    using System.Runtime.CompilerServices;
    using System.Runtime.InteropServices;

    sealed internal class ColumnBinding {

        // shared with other ColumnBindings
        private readonly OleDbDataReader _dataReader; // HCHAPTER
        private readonly RowBinding _rowbinding; // for native buffer interaction
        private readonly Bindings _bindings;

        // unique to this ColumnBinding
        private readonly OleDbParameter _parameter; // output value
        private readonly int _parameterChangeID;
        private readonly int _offsetStatus;
        private readonly int _offsetLength;
        private readonly int _offsetValue;

        private readonly int _ordinal;
        private readonly int _maxLen;
        private readonly short _wType;
        private readonly byte _precision;

        private readonly int _index;
        private readonly int _indexForAccessor;    // HCHAPTER
        private readonly int _indexWithinAccessor; // HCHAPTER

        private readonly bool _ifIRowsetElseIRow;

        // unique per current input value
        private int _valueBindingOffset;
        private int _valueBindingSize;
        internal StringMemHandle _sptr;
        private GCHandle _pinnedBuffer;

        // value is cached via property getters so the original may be released
        // for Value, ValueByteArray, ValueString, ValueVariant
        private object _value;

        internal ColumnBinding(OleDbDataReader dataReader, int index, int indexForAccessor, int indexWithinAccessor,
                                OleDbParameter parameter, RowBinding rowbinding, Bindings bindings, tagDBBINDING binding, int offset,
                                bool ifIRowsetElseIRow) {

            Debug.Assert(null != rowbinding, "null rowbinding");
            Debug.Assert(null != bindings, "null bindings");
            Debug.Assert(ODB.SizeOf_tagDBBINDING <= offset, "invalid offset" + offset);

            _dataReader = dataReader;
            _rowbinding = rowbinding;
            _bindings = bindings;
            _index = index;
            _indexForAccessor = indexForAccessor;
            _indexWithinAccessor = indexWithinAccessor;

            if (null != parameter) {
                _parameter = parameter;
                _parameterChangeID = parameter.ChangeID;
            }
            _offsetStatus = binding.obStatus.ToInt32() + offset;
            _offsetLength = binding.obLength.ToInt32() + offset;
            _offsetValue  = binding.obValue.ToInt32() + offset;

            Debug.Assert(0 <= _offsetStatus, "negative _offsetStatus");
            Debug.Assert(0 <= _offsetLength, "negative _offsetLength");
            Debug.Assert(0 <= _offsetValue,  "negative _offsetValue");

            _ordinal = binding.iOrdinal.ToInt32();
            _maxLen = binding.cbMaxLen.ToInt32();
            _wType = binding.wType;
            _precision = binding.bPrecision;

            _ifIRowsetElseIRow = ifIRowsetElseIRow;

            SetSize(Bindings.ParamSize.ToInt32());
        }

        internal Bindings Bindings {
            get {
                _bindings.CurrentIndex = IndexWithinAccessor;
                return _bindings;
            }
        }

        internal RowBinding RowBinding {
             get { return _rowbinding; }
        }

        internal int ColumnBindingOrdinal {
            get { return _ordinal; }
        }

        private int ColumnBindingMaxLen {
            get { return _maxLen; }
        }

        private byte ColumnBindingPrecision {
            get { return _precision; }
        }

        private short DbType {
            get { return _wType; }
        }

        private Type ExpectedType {
            get { return NativeDBType.FromDBType(DbType, false, false).dataType; }
        }

        internal int Index {
            get { return _index; }
        }
        internal int IndexForAccessor {
            get { return _indexForAccessor; }
        }

        internal int IndexWithinAccessor {
            get { return _indexWithinAccessor; }
        }

        private int ValueBindingOffset { // offset within the value of where to start copying
            get { return _valueBindingOffset; }
        }

        private int ValueBindingSize { // maximum size of the value to copy
            get { return _valueBindingSize; }
        }

        internal int ValueOffset { // offset within the native buffer to put the value
            get { return _offsetValue; }
        }

        private OleDbDataReader DataReader() {
            Debug.Assert(null != _dataReader, "null DataReader");
            return _dataReader;
        }

        internal bool IsParameterBindingInvalid(OleDbParameter parameter) {
            Debug.Assert((null != _parameter) && (null != parameter), "null parameter");
            return ((_parameter.ChangeID != _parameterChangeID) || (_parameter != parameter));
        }

        internal bool IsValueNull() {
            return ((DBStatus.S_ISNULL == StatusValue())
                    || (((NativeDBType.VARIANT == DbType) || (NativeDBType.PROPVARIANT == DbType))
                        && (Convert.IsDBNull(ValueVariant()))));
        }

        private int LengthValue() {
            int length;
            if (_ifIRowsetElseIRow) {
                length = RowBinding.ReadIntPtr(_offsetLength).ToInt32();
            }
            else { // WebData 94427
                length = Bindings.DBColumnAccess[IndexWithinAccessor].cbDataLen.ToInt32();
            }
            return Math.Max(length, 0);
        }
        private void LengthValue(int value) {
            Debug.Assert(0 <= value, "negative LengthValue");
            RowBinding.WriteIntPtr(_offsetLength, (IntPtr)value);
        }

        internal OleDbParameter Parameter() {
            Debug.Assert(null != _parameter, "null parameter");
            return _parameter;
        }

        internal void ResetValue() {
            _value = null;

            StringMemHandle sptr = _sptr;
            _sptr = null;

            if (null != sptr) {
                sptr.Dispose();
            }

            if (_pinnedBuffer.IsAllocated) {
                _pinnedBuffer.Free();
            }
        }

        internal DBStatus StatusValue() {
            if (_ifIRowsetElseIRow) {
                return (DBStatus) RowBinding.ReadInt32(_offsetStatus);
            }
            else { // WebData 94427
                return (DBStatus) Bindings.DBColumnAccess[IndexWithinAccessor].dwStatus;
            }
        }
        internal void StatusValue(DBStatus value) {
            #if DEBUG
            switch(value) {
            case DBStatus.S_OK:
            case DBStatus.S_ISNULL:
            case DBStatus.S_DEFAULT:
                break;
            default:
                Debug.Assert(false, "unexpected StatusValue");
                break;
            }
            #endif
            RowBinding.WriteInt32(_offsetStatus, (int)value);
        }

        internal void SetOffset(int offset) {
            if (0 > offset) {
                throw ADP.InvalidOffsetValue(offset);
            }
            _valueBindingOffset = Math.Max(offset, 0);
        }

        internal void SetSize(int size) {
            _valueBindingSize = Math.Max(size, 0);
        }

        private void SetValueDBNull() {
            LengthValue(0);
            StatusValue(DBStatus.S_ISNULL);
            RowBinding.WriteInt64(ValueOffset, 0); // safe because AlignDataSize forces 8 byte blocks
        }
        private void SetValueEmpty() {
            LengthValue(0);
            StatusValue(DBStatus.S_DEFAULT);
            RowBinding.WriteInt64(ValueOffset, 0); // safe because AlignDataSize forces 8 byte blocks
        }

        internal Object Value() {
            object value = _value;
            if (null == value) {
                switch(StatusValue()) {
                case DBStatus.S_OK:
                    switch(DbType) {
                    case NativeDBType.EMPTY:
                    case NativeDBType.NULL:
                        value = DBNull.Value;
                        break;
                    case NativeDBType.I2:
                        value = Value_I2(); // Int16
                        break;
                    case NativeDBType.I4:
                        value = Value_I4(); // Int32
                        break;
                    case NativeDBType.R4:
                        value = Value_R4(); // Single
                        break;
                    case NativeDBType.R8:
                        value = Value_R8(); // Double
                        break;
                    case NativeDBType.CY:
                        value = Value_CY(); // Decimal
                        break;
                    case NativeDBType.DATE:
                        value = Value_DATE(); // DateTime
                        break;
                    case NativeDBType.BSTR:
                        value = Value_BSTR(); // String
                        break;
                    case NativeDBType.IDISPATCH:
                        value = Value_IDISPATCH(); // Object
                        break;
                    case NativeDBType.ERROR:
                        value = Value_ERROR(); // Int32
                        break;
                    case NativeDBType.BOOL:
                        value = Value_BOOL(); // Boolean
                        break;
                    case NativeDBType.VARIANT:
                        value = Value_VARIANT(); // Object
                        break;
                    case NativeDBType.IUNKNOWN:
                        value = Value_IUNKNOWN(); // Object
                        break;
                    case NativeDBType.DECIMAL:
                        value = Value_DECIMAL(); // Decimal
                        break;
                    case NativeDBType.I1:
                        value = (short) Value_I1(); // SByte->Int16
                        break;
                    case NativeDBType.UI1:
                        value = Value_UI1(); // Byte
                        break;
                    case NativeDBType.UI2:
                        value = (int) Value_UI2(); // UInt16->Int32
                        break;
                    case NativeDBType.UI4:
                        value = (long) Value_UI4(); // UInt32->Int64
                        break;
                    case NativeDBType.I8:
                        value = Value_I8(); // Int64
                        break;
                    case NativeDBType.UI8:
                        value = (Decimal) Value_UI8(); // UInt64->Decimal
                        break;
                    case NativeDBType.FILETIME:
                        value = Value_FILETIME(); // DateTime
                        break;
                    case NativeDBType.GUID:
                        value = Value_GUID(); // Guid
                        break;
                    case NativeDBType.BYTES:
                        value = Value_BYTES(); // Byte[]
                        break;
                    case NativeDBType.WSTR:
                        value = Value_WSTR(); // String
                        break;
                    case NativeDBType.NUMERIC:
                        value = Value_NUMERIC(); // Decimal
                        break;
                    case NativeDBType.DBDATE:
                        value = Value_DBDATE(); // DateTime
                        break;
                    case NativeDBType.DBTIME:
                        value = Value_DBTIME(); // TimeSpan
                        break;
                    case NativeDBType.DBTIMESTAMP:
                        value = Value_DBTIMESTAMP(); // DateTime
                        break;
                    case NativeDBType.PROPVARIANT:
                        value = Value_VARIANT(); // Object
                        break;
                    case NativeDBType.HCHAPTER:
                        value = Value_HCHAPTER(); // OleDbDataReader
                        break;
                    case (NativeDBType.BYREF | NativeDBType.BYTES):
                        value = Value_ByRefBYTES();
                        break;
                    case (NativeDBType.BYREF | NativeDBType.WSTR):
                        value = Value_ByRefWSTR();
                        break;
                    default:
                        throw ODB.GVtUnknown(DbType);
#if DEBUG
                    case NativeDBType.STR:
                        Debug.Assert(false, "should have bound as WSTR");
                        goto default;
                    case NativeDBType.VARNUMERIC:
                        Debug.Assert(false, "should have bound as NUMERIC");
                        goto default;
                    case NativeDBType.UDT:
                        Debug.Assert(false, "UDT binding should not have been encountered");
                        goto default;
                    case (NativeDBType.BYREF | NativeDBType.STR):
                        Debug.Assert(false, "should have bound as BYREF|WSTR");
                        goto default;
#endif
                    }
                    break;
                case DBStatus.S_TRUNCATED:
                    switch(DbType) {
                    case NativeDBType.BYTES:
                        value = Value_BYTES();
                        break;
                    case NativeDBType.WSTR:
                        value = Value_WSTR();
                        break;
                    case (NativeDBType.BYREF | NativeDBType.BYTES):
                        value = Value_ByRefBYTES();
                        break;
                    case (NativeDBType.BYREF | NativeDBType.WSTR):
                        value = Value_ByRefWSTR();
                        break;
                    default:
                        throw ODB.GVtUnknown(DbType);
#if DEBUG
                    case NativeDBType.STR:
                        Debug.Assert(false, "should have bound as WSTR");
                        goto default;
                    case (NativeDBType.BYREF | NativeDBType.STR):
                        Debug.Assert(false, "should have bound as BYREF|WSTR");
                        goto default;
#endif
                    }
                    break;
                case DBStatus.S_ISNULL:
                case DBStatus.S_DEFAULT:
                    value = DBNull.Value;
                    break;
                default:
                    throw CheckTypeValueStatusValue(); // MDAC 71644
                }
                _value = value;
            }
            return value;
        }
        internal void Value(object value) {
            if (null == value) {
                SetValueEmpty();
            }
            else if (Convert.IsDBNull(value)) {
                SetValueDBNull();
            }
            else switch (DbType) {
                case NativeDBType.EMPTY:
                    SetValueEmpty();
                    break;
                case NativeDBType.NULL: // language null - no representation, use DBNull
                    SetValueDBNull();
                    break;
                case NativeDBType.I2:
                    Value_I2((Int16) value);
                    break;
                case NativeDBType.I4:
                    Value_I4((Int32) value);
                    break;
                case NativeDBType.R4:
                    Value_R4((Single) value);
                    break;
                case NativeDBType.R8:
                    Value_R8((Double) value);
                    break;
                case NativeDBType.CY:
                    Value_CY((Decimal) value);
                    break;
                case NativeDBType.DATE:
                    Value_DATE((DateTime) value);
                    break;
                case NativeDBType.BSTR:
                    Value_BSTR((String) value);
                    break;
                case NativeDBType.IDISPATCH:
                    Value_IDISPATCH(value);
                    break;
                case NativeDBType.ERROR:
                    Value_ERROR((Int32) value);
                    break;
                case NativeDBType.BOOL:
                    Value_BOOL((Boolean) value);
                    break;
                case NativeDBType.VARIANT:
                    Value_VARIANT(value);
                    break;
                case NativeDBType.IUNKNOWN:
                    Value_IUNKNOWN(value);
                    break;
                case NativeDBType.DECIMAL:
                    Value_DECIMAL((Decimal) value);
                    break;
                case NativeDBType.I1:
                    if (value is Int16) { // MDAC 60430
                        Value_I1(Convert.ToSByte((Int16)value, CultureInfo.InvariantCulture));
                    }
                    else {
                        Value_I1((SByte) value);
                    }
                    break;
                case NativeDBType.UI1:
                    Value_UI1((Byte) value);
                    break;
                case NativeDBType.UI2:
                    if (value is Int32) {
                        Value_UI2(Convert.ToUInt16((Int32)value, CultureInfo.InvariantCulture));
                    }
                    else {
                        Value_UI2((UInt16) value);
                    }
                    break;
                case NativeDBType.UI4:
                    if (value is Int64) {
                        Value_UI4(Convert.ToUInt32((Int64)value, CultureInfo.InvariantCulture));
                    }
                    else {
                        Value_UI4((UInt32) value);
                    }
                    break;
                case NativeDBType.I8:
                    Value_I8((Int64) value);
                    break;
                case NativeDBType.UI8:
                    if (value is Decimal) {
                        Value_UI8(Convert.ToUInt64((Decimal)value, CultureInfo.InvariantCulture));
                    }
                    else {
                        Value_UI8((UInt64) value);
                    }
                    break;
                case NativeDBType.FILETIME:
                    Value_FILETIME((DateTime) value);
                    break;
                case NativeDBType.GUID:
                    Value_GUID((Guid) value);
                    break;
                case NativeDBType.BYTES:
                    Value_BYTES((Byte[]) value);
                    break;
                case NativeDBType.WSTR:
                    if (value is string) {
                        Value_WSTR((String) value);
                    }
                    else {
                        Value_WSTR((char[]) value);
                    }
                    break;
                case NativeDBType.NUMERIC:
                    Value_NUMERIC((Decimal) value);
                    break;
                case NativeDBType.DBDATE:
                    Value_DBDATE((DateTime) value);
                    break;
                case NativeDBType.DBTIME:
                    Value_DBTIME((TimeSpan) value);
                    break;
                case NativeDBType.DBTIMESTAMP:
                    Value_DBTIMESTAMP((DateTime) value);
                    break;
                case NativeDBType.PROPVARIANT:
                    Value_VARIANT(value);
                    break;
                case (NativeDBType.BYREF | NativeDBType.BYTES):
                    Value_ByRefBYTES((Byte[]) value);
                    break;
                case (NativeDBType.BYREF | NativeDBType.WSTR):
                    if (value is string) {
                        Value_ByRefWSTR((String) value);
                    }
                    else {
                        Value_ByRefWSTR((char[])value);
                    }
                    break;
                default:
                    Debug.Assert(false, "unknown DBTYPE");
                    throw ODB.SVtUnknown(DbType);
#if DEBUG
                case NativeDBType.STR:
                    Debug.Assert(false, "Should have bound as WSTR");
                    goto default;
                case NativeDBType.UDT:
                    Debug.Assert(false, "UDT binding should not have been encountered");
                    goto default;
                case NativeDBType.HCHAPTER:
                    Debug.Assert(false, "not allowed to set HCHAPTER");
                    goto default;
                case NativeDBType.VARNUMERIC:
                    Debug.Assert(false, "should have bound as NUMERIC");
                    goto default;
                case (NativeDBType.BYREF | NativeDBType.STR):
                    Debug.Assert(false, "should have bound as BYREF|WSTR");
                    goto default;
#endif
            }
        }

        internal Boolean Value_BOOL() {
            Debug.Assert((NativeDBType.BOOL == DbType), "Value_BOOL");
            Debug.Assert((DBStatus.S_OK == StatusValue()), "Value_BOOL");
            Int16 value = RowBinding.ReadInt16(ValueOffset);
            return (0 != value);
        }
        private void Value_BOOL(Boolean value) {
            Debug.Assert((NativeDBType.BOOL == DbType), "Value_BOOL");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt16(ValueOffset, (short)(value ? ODB.VARIANT_TRUE : ODB.VARIANT_FALSE));
        }

        private String Value_BSTR() {
            Debug.Assert((NativeDBType.BSTR == DbType), "Value_BSTR");
            Debug.Assert((DBStatus.S_OK == StatusValue()), "Value_BSTR");
            string value = "";
            RowBinding bindings = RowBinding;
            bool mustRelease = false;
            RuntimeHelpers.PrepareConstrainedRegions();
            try {
                bindings.DangerousAddRef(ref mustRelease);
                IntPtr ptr = bindings.ReadIntPtr(ValueOffset);
                if (ADP.PtrZero != ptr) {
                    value = Marshal.PtrToStringBSTR(ptr);
                }
            }
            finally {
                if (mustRelease) {
                    bindings.DangerousRelease();
                }
            }
            return value;
        }
        private void Value_BSTR(String value) {
            Debug.Assert((null != value), "Value_BSTR null");
            Debug.Assert((NativeDBType.BSTR == DbType), "Value_BSTR");
            LengthValue(value.Length * 2); /* bytecount*/
            StatusValue(DBStatus.S_OK);
            RowBinding.SetBstrValue(ValueOffset, value);
        }

        private Byte[] Value_ByRefBYTES() {
            Debug.Assert(((NativeDBType.BYREF | NativeDBType.BYTES) == DbType), "Value_ByRefBYTES");
            Debug.Assert((DBStatus.S_OK == StatusValue()), "Value_ByRefBYTES");
            byte[] value = null;
            RowBinding bindings = RowBinding;
            bool mustRelease = false;
            RuntimeHelpers.PrepareConstrainedRegions();
            try {
                bindings.DangerousAddRef(ref mustRelease);
                IntPtr ptr = bindings.ReadIntPtr(ValueOffset);
                if (ADP.PtrZero != ptr) {
                    value = new byte[LengthValue()];
                    Marshal.Copy(ptr, value, 0, value.Length);
                }
            }
            finally {
                if (mustRelease) {
                    bindings.DangerousRelease();
                }
            }
            return ((null != value) ? value : new byte[0]);
        }
        private void Value_ByRefBYTES(Byte[] value) {
            Debug.Assert(null != value, "Value_ByRefBYTES null");
            Debug.Assert((NativeDBType.BYREF | NativeDBType.BYTES) == DbType, "Value_ByRefBYTES");

            // we expect the provider/server to apply the silent truncation when binding BY_REF
            // if (value.Length < ValueBindingOffset) { throw "Offset must refer to a location within the value" }
            int length = ((ValueBindingOffset < value.Length) ? (value.Length - ValueBindingOffset) : 0);
            LengthValue(((0 < ValueBindingSize) ? Math.Min(ValueBindingSize, length) : length));
            StatusValue(DBStatus.S_OK);

            IntPtr ptr = ADP.PtrZero;
            if (0 < length) { // avoid pinning empty byte[]
                _pinnedBuffer = GCHandle.Alloc(value, GCHandleType.Pinned);
                ptr = _pinnedBuffer.AddrOfPinnedObject();
                ptr = ADP.IntPtrOffset(ptr, ValueBindingOffset);
            }
            RowBinding.SetByRefValue(ValueOffset, ptr);
        }

        private String Value_ByRefWSTR() {
            Debug.Assert((NativeDBType.BYREF | NativeDBType.WSTR) == DbType, "Value_ByRefWSTR");
            Debug.Assert((DBStatus.S_OK == StatusValue()) || (DBStatus.S_TRUNCATED == StatusValue()), "Value_ByRefWSTR");
            string value = "";
            RowBinding bindings = RowBinding;
            bool mustRelease = false;
            RuntimeHelpers.PrepareConstrainedRegions();
            try {
                bindings.DangerousAddRef(ref mustRelease);
                IntPtr ptr = bindings.ReadIntPtr(ValueOffset);
                if (ADP.PtrZero != ptr) {
                    int charCount = LengthValue() / 2;
                    value = Marshal.PtrToStringUni(ptr, charCount);
                }
            }
            finally {
                if (mustRelease) {
                    bindings.DangerousRelease();
                }
            }
            return value;
        }
        private void Value_ByRefWSTR(String value) {
            Debug.Assert(null != value, "Value_ByRefWSTR null");
            Debug.Assert((NativeDBType.BYREF | NativeDBType.WSTR) == DbType, "Value_ByRefWSTR");
            // we expect the provider/server to apply the silent truncation when binding BY_REF
            // if (value.Length < ValueBindingOffset) { throw "Offset must refer to a location within the value" }
            int length = ((ValueBindingOffset < value.Length) ? (value.Length - ValueBindingOffset) : 0);
            LengthValue(((0 < ValueBindingSize) ? Math.Min(ValueBindingSize, length) : length) * 2); /* charcount->bytecount*/
            StatusValue(DBStatus.S_OK);

            IntPtr ptr = ADP.PtrZero;
            if (0 < length) { // avoid pinning empty string, i.e String.Empty
                _pinnedBuffer = GCHandle.Alloc(value, GCHandleType.Pinned);
                ptr = _pinnedBuffer.AddrOfPinnedObject();
                ptr = ADP.IntPtrOffset(ptr, ValueBindingOffset);
            }
            RowBinding.SetByRefValue(ValueOffset, ptr);
        }
        private void Value_ByRefWSTR(char[] value) {
            Debug.Assert(null != value, "Value_ByRefWSTR null");
            Debug.Assert((NativeDBType.BYREF | NativeDBType.WSTR) == DbType, "Value_ByRefWSTR");
            // we expect the provider/server to apply the silent truncation when binding BY_REF
            // if (value.Length < ValueBindingOffset) { throw "Offset must refer to a location within the value" }
            int length = ((ValueBindingOffset < value.Length) ? (value.Length - ValueBindingOffset) : 0);
            LengthValue(((0 < ValueBindingSize) ? Math.Min(ValueBindingSize, length) : length) * 2); /* charcount->bytecount*/
            StatusValue(DBStatus.S_OK);

            IntPtr ptr = ADP.PtrZero;
            if (0 < length) { // avoid pinning empty char[]
                _pinnedBuffer = GCHandle.Alloc(value, GCHandleType.Pinned);
                ptr = _pinnedBuffer.AddrOfPinnedObject();
                ptr = ADP.IntPtrOffset(ptr, ValueBindingOffset);
            }
            RowBinding.SetByRefValue(ValueOffset, ptr);
        }
        
        private Byte[] Value_BYTES() {
            Debug.Assert(NativeDBType.BYTES == DbType, "Value_BYTES");
            Debug.Assert((DBStatus.S_OK == StatusValue()) || (DBStatus.S_TRUNCATED == StatusValue()), "Value_BYTES");
            int byteCount = Math.Min(LengthValue(), ColumnBindingMaxLen);
            byte[] value = new byte[byteCount];
            RowBinding.ReadBytes(ValueOffset, value, 0, byteCount);
            return value;
        }
        private void Value_BYTES(Byte[] value) {
            Debug.Assert(null != value, "Value_BYTES null");
            // we silently truncate when the user has specified a given Size
            int bytecount = ((ValueBindingOffset < value.Length) ? Math.Min(value.Length - ValueBindingOffset, ColumnBindingMaxLen) : 0); // 70232
            LengthValue(bytecount);
            StatusValue(DBStatus.S_OK);
            if (0 < bytecount) {
                RowBinding.WriteBytes(ValueOffset, value, ValueBindingOffset, bytecount);
            }
        }

        private Decimal Value_CY() {
            Debug.Assert(NativeDBType.CY == DbType, "Value_CY");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_CY");
            return Decimal.FromOACurrency(RowBinding.ReadInt64(ValueOffset));
        }
        private void Value_CY(Decimal value) {
            Debug.Assert(NativeDBType.CY == DbType, "Value_CY");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt64(ValueOffset, Decimal.ToOACurrency(value));
        }

        private DateTime Value_DATE() {
            Debug.Assert(NativeDBType.DATE == DbType, "Value_DATE");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_DATE");
            return DateTime.FromOADate(RowBinding.ReadDouble(ValueOffset));
        }
        private void Value_DATE(DateTime value) {
            Debug.Assert(NativeDBType.DATE == DbType, "Value_DATE");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteDouble(ValueOffset, value.ToOADate());
        }

        private DateTime Value_DBDATE() {
            Debug.Assert(NativeDBType.DBDATE == DbType, "Value_DBDATE");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_DBDATE");
            return RowBinding.ReadDate(ValueOffset);
        }
        private void Value_DBDATE(DateTime value) {
            Debug.Assert(NativeDBType.DBDATE == DbType, "Value_DATE");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteDate(ValueOffset, value);
        }

        private TimeSpan Value_DBTIME() {
            Debug.Assert(NativeDBType.DBTIME == DbType, "Value_DBTIME");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_DBTIME");
            return RowBinding.ReadTime(ValueOffset);
        }
        private void Value_DBTIME(TimeSpan value) {
            Debug.Assert(NativeDBType.DBTIME == DbType, "Value_DBTIME");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteTime(ValueOffset, value);
        }

        private DateTime Value_DBTIMESTAMP() {
            Debug.Assert(NativeDBType.DBTIMESTAMP == DbType, "Value_DBTIMESTAMP");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_DBTIMESTAMP");
            return RowBinding.ReadDateTime(ValueOffset);
        }
        private void Value_DBTIMESTAMP(DateTime value) {
            Debug.Assert(NativeDBType.DBTIMESTAMP == DbType, "Value_DBTIMESTAMP");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteDateTime(ValueOffset, value);
        }

        private Decimal Value_DECIMAL() {
            Debug.Assert(NativeDBType.DECIMAL == DbType, "Value_DECIMAL");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_DECIMAL");
            int[] buffer = new int[4];
            RowBinding.ReadInt32Array(ValueOffset, buffer, 0, 4);
            return new Decimal(
                buffer[2],  // low
                buffer[3],  // mid
                buffer[1],  // high
                (0 != (buffer[0] & unchecked((int)0x80000000))), // sign
                unchecked((byte)((buffer[0] & unchecked((int)0x00FF0000)) >> 16))); // scale, MDAC 95080
        }
        private void Value_DECIMAL(Decimal value) {
            Debug.Assert(NativeDBType.DECIMAL == DbType, "Value_DECIMAL");

            /* pending breaking change approval
            if (_precision < ((System.Data.SqlTypes.SqlDecimal) value).Precision) { // WebData 87236
                throw ADP.ParameterValueOutOfRange(value);
            }
            */

            LengthValue(0);
            StatusValue(DBStatus.S_OK);

            int[] tmp = Decimal.GetBits(value);
            int[] buffer = new int[4] {
                tmp[3], tmp[2], tmp[0], tmp[1]
            };
            RowBinding.WriteInt32Array(ValueOffset, buffer, 0, 4);
        }

        private Int32 Value_ERROR() {
            Debug.Assert(NativeDBType.ERROR == DbType, "Value_ERROR");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_ERROR");
            return RowBinding.ReadInt32(ValueOffset);
        }
        private void Value_ERROR(Int32 value) {
            Debug.Assert(NativeDBType.ERROR == DbType, "Value_ERROR");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt32(ValueOffset, value);
        }

        private DateTime Value_FILETIME() {
            Debug.Assert(NativeDBType.FILETIME == DbType, "Value_FILETIME");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_FILETIME");
            Int64 tmp = RowBinding.ReadInt64(ValueOffset);
            return DateTime.FromFileTime(tmp);
        }
        private void Value_FILETIME(DateTime value) {
            Debug.Assert(NativeDBType.FILETIME == DbType, "Value_FILETIME");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            Int64 tmp = value.ToFileTime();
            RowBinding.WriteInt64(ValueOffset, tmp);
        }

        internal Guid Value_GUID() {
            Debug.Assert(NativeDBType.GUID == DbType, "Value_GUID");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_GUID");
            return RowBinding.ReadGuid(ValueOffset);
        }
        private void Value_GUID(Guid value) {
            Debug.Assert(NativeDBType.GUID == DbType, "Value_GUID");

            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteGuid(ValueOffset, value);
        }

        internal OleDbDataReader Value_HCHAPTER() {
            Debug.Assert(NativeDBType.HCHAPTER == DbType, "Value_HCHAPTER");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_HCHAPTER");
            
            return DataReader().ResetChapter(IndexForAccessor, IndexWithinAccessor, RowBinding, ValueOffset);
        }
        
        private SByte Value_I1() {
            Debug.Assert(NativeDBType.I1 == DbType, "Value_I1");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_I1");
            byte value = RowBinding.ReadByte(ValueOffset);
            return unchecked((SByte)value);
        }
        private void Value_I1(SByte value) {
            Debug.Assert(NativeDBType.I1 == DbType, "Value_I1");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteByte(ValueOffset, unchecked((Byte) value));
        }

        internal Int16 Value_I2() {
            Debug.Assert(NativeDBType.I2 == DbType, "Value_I2");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_I2");
            return RowBinding.ReadInt16(ValueOffset);
        }
        private void Value_I2(Int16 value) {
            Debug.Assert(NativeDBType.I2 == DbType, "Value_I2");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt16(ValueOffset, value);
        }

        private Int32 Value_I4() {
            Debug.Assert(NativeDBType.I4 == DbType, "Value_I4");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_I4");
            return RowBinding.ReadInt32(ValueOffset);
        }
        private void Value_I4(Int32 value) {
            Debug.Assert(NativeDBType.I4 == DbType, "Value_I4");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt32(ValueOffset, value);
        }

        private Int64 Value_I8() {
            Debug.Assert(NativeDBType.I8 == DbType, "Value_I8");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_I8");
            return RowBinding.ReadInt64(ValueOffset);
        }
        private void Value_I8(Int64 value) {
            Debug.Assert(NativeDBType.I8 == DbType, "Value_I8");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt64(ValueOffset, value);
        }

        private object Value_IDISPATCH() {
            Debug.Assert(NativeDBType.IDISPATCH == DbType, "Value_IDISPATCH");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_IDISPATCH");
            object value;
            RowBinding bindings = RowBinding;
            bool mustRelease = false;
            RuntimeHelpers.PrepareConstrainedRegions();
            try {
                bindings.DangerousAddRef(ref mustRelease);
                IntPtr ptr = bindings.ReadIntPtr(ValueOffset);
                value = Marshal.GetObjectForIUnknown(ptr);
            }
            finally {
                if (mustRelease) {
                    bindings.DangerousRelease();
                }
            }
            return value;
        }
        private void Value_IDISPATCH(object value) {
            // 
            (new System.Security.NamedPermissionSet("FullTrust")).Demand(); // MDAC 80727
            Debug.Assert(NativeDBType.IDISPATCH == DbType, "Value_IDISPATCH");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            IntPtr ptr = Marshal.GetIDispatchForObject(value); // MDAC 80727
            RowBinding.WriteIntPtr(ValueOffset, ptr);
        }

        private object Value_IUNKNOWN() {
            Debug.Assert(NativeDBType.IUNKNOWN == DbType, "Value_IUNKNOWN");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_IUNKNOWN");
            object value;
            RowBinding bindings = RowBinding;
            bool mustRelease = false;
            RuntimeHelpers.PrepareConstrainedRegions();
            try {
                bindings.DangerousAddRef(ref mustRelease);
                IntPtr ptr = bindings.ReadIntPtr(ValueOffset);
                value = Marshal.GetObjectForIUnknown(ptr);
            }
            finally {
                if (mustRelease) {
                    bindings.DangerousRelease();
                }
            }
            return value;
        }
        private void Value_IUNKNOWN(object value) {
            // 
            (new System.Security.NamedPermissionSet("FullTrust")).Demand(); // MDAC 80727
            Debug.Assert(NativeDBType.IUNKNOWN == DbType, "Value_IUNKNOWN");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            IntPtr ptr = Marshal.GetIUnknownForObject(value); // MDAC 80727
            RowBinding.WriteIntPtr(ValueOffset, ptr);
        }

        private Decimal Value_NUMERIC() {
            Debug.Assert(NativeDBType.NUMERIC == DbType, "Value_NUMERIC");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_NUMERIC");
            return RowBinding.ReadNumeric(ValueOffset);
        }
        private void Value_NUMERIC(Decimal value) {
            Debug.Assert(NativeDBType.NUMERIC == DbType, "Value_NUMERIC");

            /* pending breaking change approval
            if (_precision < ((System.Data.SqlTypes.SqlDecimal) value).Precision) { // WebData 87236
                throw ADP.ParameterValueOutOfRange(value);
            }
            */

            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteNumeric(ValueOffset, value, ColumnBindingPrecision);
        }

        private Single Value_R4() {
            Debug.Assert(NativeDBType.R4 == DbType, "Value_R4");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_R4");

            return RowBinding.ReadSingle(ValueOffset);
        }
        private void Value_R4(Single value) {
            Debug.Assert(NativeDBType.R4 == DbType, "Value_R4");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteSingle(ValueOffset,value);
        }

        private Double Value_R8() {
            Debug.Assert(NativeDBType.R8 == DbType, "Value_R8");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_R8");

            return RowBinding.ReadDouble(ValueOffset);
        }
        private void Value_R8(Double value) {
            Debug.Assert(NativeDBType.R8 == DbType, "Value_I4");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteDouble(ValueOffset, value);
        }

        private Byte Value_UI1() {
            Debug.Assert(NativeDBType.UI1 == DbType, "Value_UI1");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_UI1");
            return RowBinding.ReadByte(ValueOffset);
        }
        private void Value_UI1(Byte value) {
            Debug.Assert(NativeDBType.UI1 == DbType, "Value_UI1");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteByte(ValueOffset, value);
        }

        internal UInt16 Value_UI2() {
            Debug.Assert(NativeDBType.UI2 == DbType, "Value_UI2");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_UI2");
            return unchecked((UInt16) RowBinding.ReadInt16(ValueOffset));
        }
        private void Value_UI2(UInt16 value) {
            Debug.Assert(NativeDBType.UI2 == DbType, "Value_UI2");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt16(ValueOffset, unchecked((Int16) value));
        }

        internal UInt32 Value_UI4() {
            Debug.Assert(NativeDBType.UI4 == DbType, "Value_UI4");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_UI4");
            return unchecked((UInt32) RowBinding.ReadInt32(ValueOffset));
        }
        private void Value_UI4(UInt32 value) {
            Debug.Assert(NativeDBType.UI4 == DbType, "Value_UI4");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt32(ValueOffset, unchecked((Int32) value));
        }

        internal UInt64 Value_UI8() {
            Debug.Assert(NativeDBType.UI8 == DbType, "Value_UI8");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_UI8");
            return unchecked((UInt64) RowBinding.ReadInt64(ValueOffset));
        }
        private void Value_UI8(UInt64 value) {
            Debug.Assert(NativeDBType.UI8 == DbType, "Value_UI8");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.WriteInt64(ValueOffset, unchecked((Int64) value));
        }

        private String Value_WSTR() {
            Debug.Assert(NativeDBType.WSTR == DbType, "Value_WSTR");
            Debug.Assert((DBStatus.S_OK == StatusValue()) || (DBStatus.S_TRUNCATED == StatusValue()), "Value_WSTR");
            Debug.Assert(2 < ColumnBindingMaxLen, "Value_WSTR");
            int byteCount = Math.Min(LengthValue(), ColumnBindingMaxLen-2);
            return RowBinding.PtrToStringUni(ValueOffset, byteCount / 2);
        }
        private void Value_WSTR(String value) {
            Debug.Assert(null != value, "Value_BYTES null");
            Debug.Assert(NativeDBType.WSTR == DbType, "Value_WSTR");
            // we silently truncate when the user has specified a given Size
            int charCount = ((ValueBindingOffset < value.Length) ? Math.Min(value.Length - ValueBindingOffset, (ColumnBindingMaxLen-2)/2) : 0); // 70232

            LengthValue(charCount*2);
            StatusValue(DBStatus.S_OK);
            if (0 < charCount) {
                char[] chars = value.ToCharArray(ValueBindingOffset, charCount);
                RowBinding.WriteCharArray(ValueOffset, chars, ValueBindingOffset, charCount);
            }
        }
        private void Value_WSTR(char[] value) {
            Debug.Assert(null != value, "Value_BYTES null");
            Debug.Assert(NativeDBType.WSTR == DbType, "Value_WSTR");
            // we silently truncate when the user has specified a given Size
            int charCount = ((ValueBindingOffset < value.Length) ? Math.Min(value.Length - ValueBindingOffset, (ColumnBindingMaxLen-2)/2) : 0); // 70232

            LengthValue(charCount*2);
            StatusValue(DBStatus.S_OK);
            if (0 < charCount) {
                RowBinding.WriteCharArray(ValueOffset, value, ValueBindingOffset, charCount);
            }
        }
        private object Value_VARIANT() {
            Debug.Assert((NativeDBType.VARIANT == DbType) || (NativeDBType.PROPVARIANT == DbType), "Value_VARIANT");
            Debug.Assert(DBStatus.S_OK == StatusValue(), "Value_VARIANT");
            return RowBinding.GetVariantValue(ValueOffset);
        }
        private void Value_VARIANT(object value) {
            Debug.Assert((NativeDBType.VARIANT == DbType) || (NativeDBType.PROPVARIANT == DbType), "Value_VARIANT");
            LengthValue(0);
            StatusValue(DBStatus.S_OK);
            RowBinding.SetVariantValue(ValueOffset, value);
        }

        internal Boolean ValueBoolean() {
            Boolean value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.BOOL:
                    value = Value_BOOL();
                    break;
                case NativeDBType.VARIANT:
                    value = (Boolean) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Boolean));
            }
            return value;
        }

        internal byte[] ValueByteArray() {
            byte[] value = (byte[]) _value;
            if (null == value) {
                switch(StatusValue()) {
                case DBStatus.S_OK:
                    switch(DbType) {
                    case NativeDBType.BYTES:
                        value = Value_BYTES(); // String
                        break;
                    case NativeDBType.VARIANT:
                        value = (byte[])ValueVariant(); // Object
                        break;
                    case (NativeDBType.BYREF | NativeDBType.BYTES):
                        value = Value_ByRefBYTES();
                        break;
                    default:
                        throw ODB.ConversionRequired();
                    }
                    break;
                case DBStatus.S_TRUNCATED:
                    switch(DbType) {
                    case NativeDBType.BYTES:
                        value = Value_BYTES();
                        break;
                    case (NativeDBType.BYREF | NativeDBType.BYTES):
                        value = Value_ByRefBYTES();
                        break;
                    default:
                        throw ODB.ConversionRequired();
                    }
                    break;
                default:
                    throw CheckTypeValueStatusValue(typeof(byte[]));
                }
                _value = value;
            }
            return value;
        }

        internal Byte ValueByte() {
            Byte value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.UI1:
                    value = Value_UI1();
                    break;
                case NativeDBType.VARIANT:
                    value = (Byte) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Byte));
            }
            return value;
        }

        internal OleDbDataReader ValueChapter() {
            OleDbDataReader value = (OleDbDataReader) _value;
            if (null == value) {
                switch(StatusValue()) {
                case DBStatus.S_OK:
                    switch(DbType) {
                    case NativeDBType.HCHAPTER:
                        value = Value_HCHAPTER(); // OleDbDataReader
                        break;
                    default:
                        throw ODB.ConversionRequired();
                    }
                    break;
                default:
                    throw CheckTypeValueStatusValue(typeof(String));
                }
                _value = value;
            }
            return value;
        }

        internal DateTime ValueDateTime() {
            DateTime value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.DATE:
                    value = Value_DATE();
                    break;
                case NativeDBType.DBDATE:
                    value = Value_DBDATE();
                    break;
                case NativeDBType.DBTIMESTAMP:
                    value = Value_DBTIMESTAMP();
                    break;
                case NativeDBType.FILETIME:
                    value = Value_FILETIME();
                    break;
                case NativeDBType.VARIANT:
                    value = (DateTime) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int16));
            }
            return value;
        }

        internal Decimal ValueDecimal() {
            Decimal value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.CY:
                    value = Value_CY();
                    break;
                case NativeDBType.DECIMAL:
                    value = Value_DECIMAL();
                    break;
                case NativeDBType.NUMERIC:
                    value = Value_NUMERIC();
                    break;
                case NativeDBType.UI8:
                    value = (Decimal)Value_UI8();
                    break;
                case NativeDBType.VARIANT:
                    value = (Decimal) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int16));
            }
            return value;
        }

        internal Guid ValueGuid() {
            Guid value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.GUID:
                    value = Value_GUID();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int16));
            }
            return value;
        }

        internal Int16 ValueInt16() {
            Int16 value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.I2:
                    value = Value_I2();
                    break;
                case NativeDBType.I1:
                    value = (Int16) Value_I1();
                    break;
                case NativeDBType.VARIANT:
                    object variant = ValueVariant();
                    if (variant is SByte) {
                        value = (Int16)(SByte) variant;
                    }
                    else {
                        value = (Int16) variant;
                    }
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int16));
            }
            return value;
        }

        internal Int32 ValueInt32() {
            Int32 value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.I4:
                    value = Value_I4();
                    break;
                case NativeDBType.UI2:
                    value = (Int32) Value_UI2();
                    break;
                case NativeDBType.VARIANT:
                    object variant = ValueVariant();
                    if (variant is UInt16) {
                        value = (Int32)(UInt16) variant;
                    }
                    else {
                        value = (Int32) variant;
                    }
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int32));
            }
            return value;
        }

        internal Int64 ValueInt64() {
            Int64 value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.I8:
                    value = Value_I8();
                    break;
                case NativeDBType.UI4:
                    value = (Int64) Value_UI4();
                    break;
                case NativeDBType.VARIANT:
                    object variant = ValueVariant();
                    if (variant is UInt32) {
                        value = (Int64)(UInt32) variant;
                    }
                    else {
                        value = (Int64) variant;
                    }
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Int64));
            }
            return value;
        }

        internal Single ValueSingle() {
            Single value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.R4:
                    value = Value_R4();
                    break;
                case NativeDBType.VARIANT:
                    value = (Single) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Single));
            }
            return value;
        }

        internal Double ValueDouble() {
            Double value;
            switch(StatusValue()) {
            case DBStatus.S_OK:
                switch(DbType) {
                case NativeDBType.R8:
                    value = Value_R8();
                    break;
                case NativeDBType.VARIANT:
                    value = (Double) ValueVariant();
                    break;
                default:
                    throw ODB.ConversionRequired();
                }
                break;
            default:
                throw CheckTypeValueStatusValue(typeof(Double));
            }
            return value;
        }

        internal string ValueString() {
            string value = (String) _value;
            if (null == value) {
                switch(StatusValue()) {
                case DBStatus.S_OK:
                    switch(DbType) {
                    case NativeDBType.BSTR:
                        value = Value_BSTR(); // String
                        break;
                    case NativeDBType.VARIANT:
                        value = (String) ValueVariant(); // Object
                        break;
                    case NativeDBType.WSTR:
                        value = Value_WSTR(); // String
                        break;
                    case (NativeDBType.BYREF | NativeDBType.WSTR):
                        value = Value_ByRefWSTR();
                        break;
                    default:
                        throw ODB.ConversionRequired();
                    }
                    break;
                case DBStatus.S_TRUNCATED:
                    switch(DbType) {
                    case NativeDBType.WSTR:
                        value = Value_WSTR();
                        break;
                    case (NativeDBType.BYREF | NativeDBType.WSTR):
                        value = Value_ByRefWSTR();
                        break;
                    default:
                        throw ODB.ConversionRequired();
                    }
                    break;
                default:
                    throw CheckTypeValueStatusValue(typeof(String));
                }
                _value = value;
            }
            return value;
        }

        private object ValueVariant() {
            object value = _value;
            if (null == value) {
                value = Value_VARIANT();
                _value = value;
            }
            return value;
        }

        private Exception CheckTypeValueStatusValue() { // MDAC 71644
            return CheckTypeValueStatusValue(ExpectedType);
        }

        private Exception CheckTypeValueStatusValue(Type expectedType) { // MDAC 71644
            switch (StatusValue()) {
            case DBStatus.S_OK:
                Debug.Assert(false, "CheckStatusValue: unhandled data with ok status");
                goto case DBStatus.E_CANTCONVERTVALUE;
            case DBStatus.S_TRUNCATED:
                Debug.Assert(false, "CheckStatusValue: unhandled data with truncated status");
                goto case DBStatus.E_CANTCONVERTVALUE;
            case DBStatus.E_BADACCESSOR:
                return ODB.BadAccessor();
            case DBStatus.E_CANTCONVERTVALUE:
                return ODB.CantConvertValue(); // 
            case DBStatus.S_ISNULL: // database null
                return ADP.InvalidCast(); // 
            case DBStatus.E_SIGNMISMATCH:
                return ODB.SignMismatch(expectedType);
            case DBStatus.E_DATAOVERFLOW:
                return ODB.DataOverflow(expectedType);
            case DBStatus.E_CANTCREATE:
                return ODB.CantCreate(expectedType);
            case DBStatus.E_UNAVAILABLE:
                return ODB.Unavailable(expectedType);
            default:
                return ODB.UnexpectedStatusValue(StatusValue());
            }
        }
    }
}
